This proposal seeks to competitively renew funding for infrastructure, personnel, and resources in support of the MMRRC at the University of California (UC) Davis (UCD-MMRRC). The UCD-MMRRC, alongside 2 centers at the University of Missouri-Columbia and University of North Carolina-Chapel Hill, and an Informatics, Coordination, and Service Center (ICSC) at The Jackson Laboratory, serves as the distribution archives and data center for the MMRRC National Program. Since its inception 10 years ago, the UCD- MMRRC has been one of the primary mutant mouse archive and distribution repositories in the world. We are the largest archive of three centers, with an inventory of over 28,500 mutant mouse lines representing ~98% of all live colonies, germplasm, and/or embryonic stem (ES) cells in the system. The UCD-MMRRC has fulfilled nearly 6000 orders from more than 2000 investigators at 500 institutions in 30 countries. We have also been a leader in innovation and resource development for the system, introducing new products (e.g., gene trap ES cells) and initiating new services (e.g., blastocyst injection, ICSI) that have added scientific value to mouse models and enhanced utilization of the MMRRC by researchers. UCD-MMRRC has leveraged its infrastructure and expertise to extend its service role by contracting with NIH institutes, biotechnology companies, and several organizations to archive, distribute, custom breed, genotype, and phenotype 1000's of additional ES cell mutants, BAC-transgenic, CRE, ENU-induced, and other mutant mouse collections. In addition, we have worked with the Centers and NIH program staff and developed and implemented advertising and marketing strategies, database management and informatics applications, website and online resources, customer and user services, operating procedures and policies, and shared governance of the national program.